The applicability of perovskite-type SrVO3-δ in high-temperature electrochemical energy conversion technology is hampered by the limited stability domain of the perovskite phase. The aim of the present work was to find a compromise between the phase stability and electrical performance by designing solid solutions in the SrVO3 -SrTiO3 system. Increasing titanium content in SrV1-y Tiy O3-δ (y=0-0.9) perovskites is demonstrated to result in a gradual shift of the upper-p(O2 ) phase stability boundary toward oxidizing conditions: from ≈10-15 bar at 900 °C for undoped SrVO3-δ to ≈10-11 -10-5 bar for y=0.3-0.5. Although the improvement in the phase stability is accompanied by a decrease in electrical conductivity, the conductivities of SrV0.7 Ti0.3 O3-δ and SrV0.5 Ti0.5 O3-δ at 900 °C remain as high as 80 and 20 S cm-1 , respectively, and is essentially independent of p(O2 ) within the phase-stability domain. Combined XRD, thermogravimetric analysis, and electrical studies revealed very sluggish kinetics of oxidation of SrV0.5 Ti0.5 O3-δ ceramics under inert gas conditions and a nearly reversible behavior after exposure to an inert atmosphere at elevated temperatures. Substitution by titanium in the SrV1-y Tiy O3-δ system results also in a decrease of oxygen deficiency in perovskite lattice and a favorable suppression of thermochemical expansion. Variations of oxygen nonstoichiometry and electrical properties in the SrV1-y Tiy O3-δ series are discussed in combination with the simulated defect chemistry of solid solutions.
Keywords: electrical conductivity; fuel cells; stability; titanates; vanadates.
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